It is relatively simple for a hostile attacker to thwart the intentions of the author of a computer program when the program is executed in a computing environment that is controlled by the attacker. Digital signature checks can be skipped and object code modified. For example, a piece of source code that is written to check that the computer program has been purchased could consist of the preposition: “if purchased, run or else fail.” An attacker can alter the object code to jump straight to the true consequence even if the antecedent is false.